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 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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package java.sql;

/**
 * The interface used for the custom mapping of an SQL user-defined type (UDT) to
 * a class in the Java programming language. The class object for a class
 * implementing the <code>SQLData</code> interface will be entered in the
 * appropriate <code>Connection</code> object's type map along with the SQL
 * name of the UDT for which it is a custom mapping.
 * <P>
 * Typically, a <code>SQLData</code> implementation
 * will define a field for each attribute of an SQL structured type or a
 * single field for an SQL <code>DISTINCT</code> type. When the UDT is
 * retrieved from a data source with the <code>ResultSet.getObject</code>
 * method, it will be mapped as an instance of this class.  A programmer
 * can operate on this class instance just as on any other object in the
 * Java programming language and then store any changes made to it by
 * calling the <code>PreparedStatement.setObject</code> method,
 * which will map it back to the SQL type.
 * <p>
 * It is expected that the implementation of the class for a custom
 * mapping will be done by a tool.  In a typical implementation, the
 * programmer would simply supply the name of the SQL UDT, the name of
 * the class to which it is being mapped, and the names of the fields to
 * which each of the attributes of the UDT is to be mapped.  The tool will use
 * this information to implement the <code>SQLData.readSQL</code> and
 * <code>SQLData.writeSQL</code> methods.  The <code>readSQL</code> method
 * calls the appropriate <code>SQLInput</code> methods to read
 * each attribute from an <code>SQLInput</code> object, and the
 * <code>writeSQL</code> method calls <code>SQLOutput</code> methods
 * to write each attribute back to the data source via an
 * <code>SQLOutput</code> object.
 * <P>
 * An application programmer will not normally call <code>SQLData</code> methods
 * directly, and the <code>SQLInput</code> and <code>SQLOutput</code> methods
 * are called internally by <code>SQLData</code> methods, not by application code.
 *
 * @since 1.2
 */
public interface SQLData {

  /**
   * Returns the fully-qualified
   * name of the SQL user-defined type that this object represents.
   * This method is called by the JDBC driver to get the name of the
   * UDT instance that is being mapped to this instance of
   * <code>SQLData</code>.
   *
   * @return the type name that was passed to the method <code>readSQL</code> when this object was
   * constructed and populated
   * @throws SQLException if there is a database access error
   * @throws SQLFeatureNotSupportedException if the JDBC driver does not support this method
   * @since 1.2
   */
  String getSQLTypeName() throws SQLException;

  /**
   * Populates this object with data read from the database.
   * The implementation of the method must follow this protocol:
   * <UL>
   * <LI>It must read each of the attributes or elements of the SQL
   * type  from the given input stream.  This is done
   * by calling a method of the input stream to read each
   * item, in the order that they appear in the SQL definition
   * of the type.
   * <LI>The method <code>readSQL</code> then
   * assigns the data to appropriate fields or
   * elements (of this or other objects).
   * Specifically, it must call the appropriate <i>reader</i> method
   * (<code>SQLInput.readString</code>, <code>SQLInput.readBigDecimal</code>,
   * and so on) method(s) to do the following:
   * for a distinct type, read its single data element;
   * for a structured type, read a value for each attribute of the SQL type.
   * </UL>
   * The JDBC driver initializes the input stream with a type map
   * before calling this method, which is used by the appropriate
   * <code>SQLInput</code> reader method on the stream.
   *
   * @param stream the <code>SQLInput</code> object from which to read the data for the value that
   * is being custom mapped
   * @param typeName the SQL type name of the value on the data stream
   * @throws SQLException if there is a database access error
   * @throws SQLFeatureNotSupportedException if the JDBC driver does not support this method
   * @see SQLInput
   * @since 1.2
   */
  void readSQL(SQLInput stream, String typeName) throws SQLException;

  /**
   * Writes this object to the given SQL data stream, converting it back to
   * its SQL value in the data source.
   * The implementation of the method must follow this protocol:<BR>
   * It must write each of the attributes of the SQL type
   * to the given output stream.  This is done by calling a
   * method of the output stream to write each item, in the order that
   * they appear in the SQL definition of the type.
   * Specifically, it must call the appropriate <code>SQLOutput</code> writer
   * method(s) (<code>writeInt</code>, <code>writeString</code>, and so on)
   * to do the following: for a Distinct Type, write its single data element;
   * for a Structured Type, write a value for each attribute of the SQL type.
   *
   * @param stream the <code>SQLOutput</code> object to which to write the data for the value that
   * was custom mapped
   * @throws SQLException if there is a database access error
   * @throws SQLFeatureNotSupportedException if the JDBC driver does not support this method
   * @see SQLOutput
   * @since 1.2
   */
  void writeSQL(SQLOutput stream) throws SQLException;
}
